Structural panel and method of production



April 8, 1969 o s 3,437,508

STRUCTURAL PANEL AND METHOD OF PRODUCTION Original Filed Sept. 28. 1966E O Q INVENTOR.

A9313 8, 1969 F. T. GORSKI STRUCTURAL PANEL AND METHOD OF PRODUCTION zof 2 Sheet INVENTOR A 7 TOR/v5 V6 United States U.S. Cl. 117-54 9 ClaimsABSTRACT OF THE DISCLOSURE Method for improving the fiber surfacesmoothness and appearance of porous fibrous panels made of discontinuousglass fibers or the like, wherein the fibers are bonded to one anotheronly at points of contact by hardened bonding material, with intersticesbetween, which comprises, coating the surface fibers with additionalliquid, hardenable material and then hardening the material in order tofirm up or stiffen the surface fibers; and then dry grinding to removefibers and thereby provide improved surface contour, while preservingthe porosity of the panel. The product is a porous panel of improvedsurface finish and smoothness.

The invention overcomes prior art defects including offware due toindentations, stains and binder spots, light density spots,off-tolerance variations in thickness and weight, and poor bevels.Process efficiencies of 15-20% improvement over the prior art have beeneffected.

This application is a continuation-in-part of application Ser. No.204,920 filed June 25, 1962, now abandoned and a continuation of Ser.No. 589,158, filed Sept. 28, 1966, now abandoned.

This invention relates to structural panels and to a method ofproduction. More particularly, this invention relates to structuralpanels having improved surface finish, scuff resistance, and sharper andcleaner bevels giving improved appearance; and, to an improved method ofhigher efficiency for producing such structural panels. Further, thisinvention relates to structural panels adapted for use as ceiling orwall coverings.

In the prior art one popular structural panel comprises a high densityboard-like mat of glass fibers bonded with a relatively heavy content ofthermosetting resin, such as phenol formaldehyde. The board is beveledat the edges and provided with a surface finish such as paint forpleasant appearance.

However, this prior product and method have been characterized byseveral defects including offware due to indentations, stains or binderspots, light density spots, off-tolerance variations in thickness andweight, and poor bevels.

The stains which appear on the product are of such nature that they arenot capable of detection at the end of the production line beforepackaging and shipment. Thus, they show up only after storage as theresult of a slow build-up.

Also, the prior product has been too soft for sharp bevels. Thus, arelatively broad or dull bevel has been necessary to reduce bevelbreak-outs and defects.

It has also been found that soft spots appear in the exposed surface ofthe prior product; these contribute to poor binder saturation andresultant stains or spots after storage.

The result is low production line efficiency because of rejects.

atent O ice Accordingly, an important step forward in the art structuralpanels for ceilings or wall applications, having improved surfacefinish, better scuff resistance, finer bevels, and wherein the methodprovides efficiencies up to 25% greater than the prior art.

It is, accordingly, an important object of the present invention toprovide an improved structural panel.

A :further object is to provide an improved structural panelcharacterized by improved surface finish.

A still further object is to provide a novel structural panel ofimproved surface finish and high acoustical properties for use onceilings or walls.

A still further object is to provide an improved structural panelcharacterized by sharper, cleaner bevels.

Another object is to provide a method for producing improved structuralpanels wherein production efficiencies up to 25 greater than the priorart are provided.

A still further object is to provide a method for producing acousticalpanels for structural purposes, such as ceilings and walls, wherein anovel pre-finish treatment is used to improve the final finishing withgreater production efficiencies.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

FIGURE 1 is a partial side elevational view of a production line for usein the present invention, showing the initial procedural steps;

FIGURE 2 is a continuation of FIGURE 1 showing the remaining proceduralsteps of the production operation;

FIGURE 3 is an enlarged fragmentary side elevational view showing onetypical, but preferred, method of applying liquid binder for treating orsaturating panels in accordance with the present invention;

FIGURE 4 is a perspective view of a panel made in accordance with thepresent invention; and,

FIGURE 5 is an enlarged fragmentary section view of a panel madeaccording to the invention.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings, since the invention is capable of otherembodiments and of being practiced or carried out in various ways. Also,it is to be understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

Perspective view In accordance with the present invention, an improvedacoustical panel of high density and made of glass fibers bonded by athermosetting resin is provided wherein the surface finish is of higherquality and the bevels are sharper and cleaner for improved appearance.

Further, in accordance with an important aspect of the method of theinvention, structural panels are formed from a high density glass fiberboard that is partially impregnated with thermosetting resin to providean improved surface for finishing by sanding, cutting, beveling andpainting operations. By so operating, greatly improved productionefiiciencies are provided.

Mat formation According to FIGURE 1, staple glass fibers comprise afoundation component of the present products. These are made by forminga plurality of small streams of molten glass and attenuating the streamsby means of a downwardly directed gas jet. The staple fibers so producedfall downwardly and are drawn by suction to a movable chain to form afibrous mat.

Thus, a glass melting furnace is provided with an elongated deliveryforehearth 12, into the bottom wall 14 of which there are fitted one ormore feeders or bushings 16. The bushings 16 comprise precious metal andare made up of generally rectangular shoe-box-like walls and bottom,being open at the top to receive molten glass flowing from the furnace.To the end walls, there are attached electrical terminals 18 to whichelectrical connections are made for passing electric current the lengthof the feeders 16 to provide proper glass feeding temperatures.

The bottom walls 20 are provided with rows of spaced tips or smalldelivery tubes 22 through which small streams 24 of molten glass issuedownwardly by gravity. Gas fiber-forming heads or attenuators 26 arepositioned beneath each of the bushings 16 and comprise spaced, parallelheaders 28 containing appropriate apertures, not shown, but ofconventional construction, adapted to produce jet-like attenuationstreams as of steam or compressed air, fed thereto from the manifoldtubes 30.

Thus, as the molten glass streams 24 issue downwardly through theattenuators 26, the high speed jets of gas grip the streams and drawthem out into very fine diameter fibers 32 of a length in the range fromabout one-fourth inch to about three inches.

A forming hood 34 is positioned beneath the fiberforming heads 26 anddirects the fibers 32 downwardly. During the downward fall of the fibers32, they are coated by sprays of aqueous thermosetting resin 36,produced from sprayheads 38 positioned in suitable apertures in theforming hood 34.

The coated fibers 40 fall downwardly through the forming hood 34 to theupper flight 31 of an endless collecting chain 44. Chain 44 is supportedby parallel and horizontally spaced rolls 46, at least one of which isdriven for moving the upper flight 42 in the arrow 48 direction.

A suction box 50, having an outlet 52, connected to a suitable exhaustfan or gas pump, is interposed between the upper flight 42 and lowerflight 54 of chain 44 to draw the coated fibers 40 downwardly onto theupper flight 42. This results in the formation of a loose mat 56 ofgradually increasing thickness, achieving full thickness as or slightlybefore it exits from the forming hood 34 on upper flight 42.

As shown in FIGURE 1, the loose mat 56 passes in the arrow 48 directionto a curing oven 58, including an outer housing or shell '60 mounted onsupports 62 and having a suitable heat source such as gas burners orelectric radiants contained therein to generate a suflicient temperaturefor curing the resin deposited by the sprays 36 to a dry condition.

To support the mat 56 during movement through the oven 58, there isprovided a lower chain or conveyor 63 having upper and lower flights 64and 66 and being mounted on axially aligned, horizontally disposed andspaced support rolls 68. One or more of the support rolls 68 is powerdriven at a synchronized line speed for movement in the previouslymentioned arrow 48 direction.

To control the thickness of the mat 56, an upper conveyor or chain 70 isprovided in parallel cooperative relationship above the lower conveyor63. The upper conveyor 70 includes a lower flight 72 and an upper flight74 with support and moving power being provided by spaced rolls 76. Thelower flight 72 is spaced an appropriate distance from upper flight 64of lower chain 63 to provide a proper mat production thickness.

From the foregoing, it Will be observed that as the loose, uncured mat56 travels through the oven 58, it will emerge as a cured mat 78 frombetween the conveyors 63 and 70. This basic cured mat 78 is ofrelatively high density, by virtue of high resin content and compactionof the fibers. The mat 78 is, however, quite porous.

Further processing of the raw matinitial sanding As shown at the rightend of FIGURE 1, the cured mat 78 passes between a support table 80 anda first dry sanding roll 82. The sanding roll 82 is effective to smooththe top surface of the cured mat 78, removing surface irregularitiessuch as flight marks made by the chain 70, to produce an initiallysanded board or mat 83.

saturating impregnation Following the initial sanding operation effectedby roll 82, the sanded mat 83 passes to the upper flight 84 of a chain86, supported on rolls '88, one or more of which is driven to drive theupper flight in synchronism with the remainder of the production line.Note the enlarged view of FIGURE 3 for details.

Between the upper flight 84- and the lower flight there is provided asuction box 92 having a narrow inlet opening 94 for appropriate suction,and an outlet opening 96, connected to a conduit leading to a suitablefan or other gas pump.

An important aspect of the present invention resides in the application,by impregnation, of a second coat of resin prior to further processing.It is important that the coating of binder applied to the surface afterthe initial sanding be drawn into the board for very uniformdistribution and fiber support. It will thus be apparent that the mat 83is quite porous.

Accordingly, as shown at the left of FIGURE 2 and in greater detail inFIGURE 3, an elongated conduit 98 is positioned above the cured andsanded mat 83 spanning the width of the mat. The weir or conduit 98 isprovided at the top with a flow slot 102 having a lower delivery edge104 over 'which a liquid resin composition 106 can fiow by gravity. Inorder to provide a sufiiciently uniform distribution across the width ofthe mat, a foraminous material 108 such as screen, woven glass cloth orthe like is provided to produce a uniform coating of downwardly flowingliquid material. To support the forarninous material 108, a bracket 110is connected along the top of the conduit 98, spanning the slot 102, andproviding a clamp portion at 112 above and adjacent to the delivery edge104. One of the longitudinal edges of the rectangular foraminous member108 is clamped at 112 so that the remainder of the member 108 falls intocontacting relationship with the side of the conduit 98 below andadjacent to the delivery edge 104 to catch the overrunning liquidmaterial 106 from the delivery edge 104 and distribute it as a uniformcurtain 114, dropping downwardly onto the upper surface of board 83.

Note that the curtain 114 deposits on the upper surface of the board 83slightly to the left of the suction throat 94 of the suction box 92.Thus, as the mat or board 83 passes over the inlet throat 94, thereduced pressure causes the material 114 to be drawn or driven uniformlyinto the mat, thus providing an impregnated mat 116.

The impregnated mat 116 passes to a second curing oven 118 that includesan outer shell 120, supported as at 122. As distinguished from the oven5-8, previously described, which included both an upper conveyor 70 anda lower conveyor 63, the second oven 118 includes only a lower conveyor124 to support the impregnated board 116. Thus, due to the fact that theboard 116 has already received a tolerable thickness by the upperconveyor 70 of oven 58, such equipment is not necessary at this point.Accordingly, the impregnated board 116 enters the oven 118 and iscarried on the upper flight 126 of conveyor 124. The conveyor 124 iscarried by spaced support rolls 130, at least one of which is powerdriven in synchronization with the production line.

Suitable heating means is provided in the oven 118 to cure theimpregnated board 116 to bone-dry state, designated 132.

Finishing As shown in FIGURE 2, the cured and dry board 132 passes to afinal sanding operation, wherein a backing table 134 cooperates with asanding roll 136. The roll 136 is elfective to reduce the thickness ofthe dry mat 132 to finished dimension.

From the sanding operation 136, 134, the finish sanded board 138 passesto one or more appropriate slitter saws 140. Following the saw 140, aknife 142, cooperating with support tables 144, finishes the cuttingoperation to provide panels of appropriate rectangular or square dimen-S1011.

From the knife 142, the blanks are beveled manually in an off-line beveloperation as at 145 and then returned to the upper flight 146 of aconveyor 148. While on the flight 146, the beveled panels pass beneathsprayheads 150 for application of paint, after which they pass through adrying oven 152. The oven 152 includes a housing 154 supported at 156and containing heating means such as gas or electrically poweredelements. A conveyor 158 spans the housing 154 and has upper and lowerflights 160 and 162 supported on rolls 164 driven at production linespeed. After emerging from oven 152, the finished blocks 166 pass alongan inspection conveyor 168 and then to a packaging station indicated bythe arrow 170.

Operation summary of the invention From the foregoing description itwill be noted that operation of the method of invention comprises animportant step of applying a partial saturating or impregnating coatingof resin to the cured and pre-sanded boards *83 and curing thisimpregnating resin to a dry state prior to finishing. By so operating,an improved base material is provided for the final grinding, bevelingand application of a surface finish paint. Thus, the production offinished panels of unexpectedly superior surface finish is effected.

It is an important and unexpected aspect of the present invention thatin contrast to analogous prior products, the bevels are shaper, cleanerand shorter, and are produced without damage, as was the experience ofthe prior art.

Finished panels of invention By reference to FIGURE 4, it will be notedthat the finished blocks 166 may be of generally square configuration inplan and are characterized by short, sharp, clean 45 bevels 172. Aspointed out above, these bevels are possible in the present product byvirtue of the improved internal structure and density of body of theboards from which made, and thus can be formed without Ebreak-outs at ahigh production rate. In order to avoid broken and crumbled edges, theprior art method required that the bevels be more flattened, thus of a30 configuration, rather than a sharp, short 45 configuration providedby the present invention. Even by so operating, due to the relativelypoor body of the prior products, rejects were relatively high because ofbeveling fractures.

Thus, it will be evident that improved structures of higher density,sharper contour lines and improved surface finish and appearance areprovided in accordance with the present invention.

Extended scope of invention While the foregoing disclosure has relatedto the use of a liquid impregnating composition containing phenolformaldehyde resin, this material is subject to some latitude of usewithin the broader scope of invention. Thus, both aqueous and alcoholicmaterials can be used. Because of the volatile nature of alcohol and thehazards of handling, water will generally be preferred. However, it hasbeen found that the alcoholic resin when applied to the boards beforepainting, will tie down potential resin stains and prevent their showingthrough the final paint.

Within the broad scope of the invention, the saturating resin may beextended to other materials such as melamine-formaldehyde,urea-formaldehyde and similar thermosetting resins.

Use of fillers for production of wall panels In an extension of theinvention, fillers such as powdered bentonite, clays, chalk, silica andthe like can be added to the impregnating resin for application to theboards, as shown at the left side of FIGURE 2 and in FIGURE 3. By sooperating, products having superior sculf and abrasion resistance forwall panel application can be made. Such materials are harder and moreresilient, but they also retain a substantial amount of acousticalefiiciency for overall sound improvement.

An enlarged cross sectional view of such a product is provided by FIGURE5 wherein it will be noted that the filler particles 174 have depositedin the upper layers of the fibers for surface support and greaterresistance against impact. The resin is shown as dots 176 of lesserdensity that have been distributed generally uniformly through theremainder of the board.

When operating in accordance with this embodiment of the invention, itis believed that the high density of the board acts as a type of filterfor the filler. Thus, the filler appears to be captured and retained inthe upper layers while the binder penetrates more deeply. This willprovide an excellent base for grinding and for subsequent finishapplication.

Paints useful for finishing in accordance with the present inventioninclude the synthetic rubber base materials, the caseins, oils and thelike. It has been found that the latex-type materials are easily appliedand sufiiciently economical that their use may be favored.

While the curtain coater 108 has been discussed with reference to thesaturation of the boards 83, it is to be understood that application ofthe saturating curtain 114 also can be made by spray guns or rollers.However, when so operating, adjustment of the applicator to provide auniform distribution throughout the mat is required and is coordinatedwith the action of the suction box 92.

The single sanding modification The extended scope of invention wouldalso encompass application of the saturating binder as by the foraminousscreen 108 prior to entry of the loose, uncured mat into the oven 58. Byso operating, the sanding can be entirely effected by the first sandingroll 82, the second roll 136 not being used. For certain types ofproducts this will provide still greater economy of operation, althoughopti mum properties are not provided as in the double sanding operationpreviously described.

Although glass fibers are preferred in the present invention, somelatitude may be tolerated as where long, staple, relatively nonbrashyfibers can be produced from other mineral materials. In addition to theuse of gas attenuated fibers, as shown in FIGURE 1, the same type ofglass fiber from other forming operations also can be used, as fromspinning plate and flame attenuation processes.

Summary and advantages From the foregoing description, it will beevident that superior products are provided in accordance with thepresent invention, characterized by sharper bevels and superior surfacefinish. Also a method giving substantially improved production lineefiiciencies is provided. In accordance with the invention, processefiiciencies of 15- 20% improvement over the prior art have beeneffected.

Another important advantage of the present invention resides in the factthat products of improved acoustical efficiency and scuff resistance areprovided.

While I do not wish to be bound by any particular theory, it is believedthat the saturation or impregnation in accordance with the inventionprovides an improved, more full-bodied surface, that is still porous,but that is 7 particularly effective for dry sanding to provide a finishreceptive surface of superior performance.

Within the scope of the invention the term grinding can be construed tobe actual fiber removal by either a sanding, grinding or abradingoperation. This is clearly distinguishable from the teaching of theprior art relating to wet sanding for the mere removal of resin in thesurface finishing of dense reinforced resin articles.

What is claimed is:

1. In a method of processing a stiff, porous, fibrous panel having anexposed, dry, fibrous, major surface and a porous, fibrous body sectionadjacent to said major surface, said panel consisting essentially ofdiscontinuous, siliceous fibers in random array, bonded to one anotherat points of contact by hardened bonding material with intersticesbetween the fibers, the steps of removing fibrous material by drygrinding from said major surface to remove irregularities,

coating the so-treated surface with additional hardenable material inliquid form to partially impregnate the surface fibers, and preservingthe porosity of the fibrous major surface and of the fibrous bodysection and moving the coating material at least partially into the bodysection, and hardening the additional material to dry condition,

and then removing additional fibrous material from said major surface bydry grinding to impart to the surface a uniform fibrous, finishedcontour.

2. In a method of processing a stiff, porous, fibrous panel having adry, fibrous major surface and a porous, fibrous body section adjacentto said major surface, said panel consisting essentially ofdiscontinuous, siliceous fibers bonded to one another at points ofcontact by hardened bonding material with interstices between thefibers, the steps of coating the major surface with additionalhardenable material in liquid form to partially impregnate the surfacefibers, and preserving the porosity of the fibrous major surface and ofthe fibrous body section, and moving the coating material at leastpartially into the body section, and hardening the additional materialto dry condition to render the surface stiffened,

and then removing fibrous material from said stiffened major surface bydry griding to remove fiber irregularities.

3. The product produced by the method of claim 2.

4. A method for imparting a finished surface of desired contour to astiff porous body of glass fibers interbonded by a hardened bindingagent comprising;

coating the surface with a hardenable material in liquid form, movingthe coating material at least partially into the body region under saidsurface, and hardening the additional material to a dry condition toimpart additional hardness to said surface,

and then mechanically working said surface in dry condition to removematerial and impart to the surface a uniform fibrous finished contour.

5. The method of claim 4 wherein the coating material is moved into theporous fibrous body region under the surface by drawing the materialtherein under the influence of a differential in gas pressure acrosssaid body region.

6. The method of claim 4 wherein the mechanical working of said surfaceto remove material is accomplished by dry grinding said surface.

7. A method for processing a stiff porous fibrous body having a dryporous surface comprising glass fibers in random array interbonded oneto another by a bonding material with interstices between the fiberscomprising;

mechanically working said porous fibrous surface in dry condition toremove surface irregularities,

coating the mechanically worked surface with hardenable material inliquid form and moving the coating material at least partially into thebody region under said surface, and hardening the additional material toa dry condition,

and then again mechanically working said surface in dry condition toremove additional material to impart to the surface a uniform fibrousfinished con tour.

8. The method of claim 7 wherein the coating material is moved into thefibrous body region under the surface by drawing the material thereinunder the influence of a differential in gas pressure across said bodyregion.

9. The method of claim 7 wherein both steps of mechanical working 'ofsaid surface to remove material are accomplished by dry grinding saidsurface.

References Cited UNITED STATES PATENTS 1/1952 Strabel 117-64 8/1962Slayter et al 26491 DONALL H. SYLVESTER, Primary Examiner.

ROBERT L. LINDSAY, Assistant Examiner.

